Experimental mice are used in various studies of diseases, and effects of experimental diets, drugs, and other treatments designed for the benefit of mankind. It is highly desirable in evaluating the effects of drugs, diet and the like, to eliminate errors and any possibility of misleading results caused by reason of a mouse urinating or defecating into its food, and thereby reinjecting the drugs or foods or metabolites thereof, normally excreted in the urine or the feces.
Furthermore, current trends in toxicology and safety evaluation concerning modern drugs and preparations have necessitated an increase in long-term feeding studies of laboratory animals undergoing tests and observations. It has been determined that long-term feeding experiments, in order to produce valid and reliable results relating to food consumption, must be conducted under extremely careful feeding conditions.
Of utmost importance is the elimination of food contamination that will occur if the animal is permitted access to food which has been exposed to animal excretions. In many instances, an animal may obtain an overdose of a drug fed to it by eating food contaminated by fecal matter or urine carrying some percentage of the original dosage, thereby inducing false test results and inaccurate observations and calculations. Moreover, in long-term feeding studies, it is essential to determine exact consumption, without losses due to spillage, while maintaining conditions of utmost cleanliness.
The early prior art feeders either permitted feed to be spilled and mixed with the bedding of the animal or permitted fecal matter to contaminate the feed. Later feeders, such as U.S. Pat. Nos. 3,114,350 and 3,505,977 have attempted to overcome these disadvantages. Although successful, such devices have necessitated the utilization of articulated screen structures or other functionally similar structures. More particularly, such prior art devices are incapable of operating in conjunction with a gravitational feeder.
The specific embodiments disclosed in Ser. No. 464,489, now U.S. Pat. No. 3,902,459, have overcome many of the defects of the prior art such as (1) providing a continuous source of feed dosed with chemical carcinogens to laboratory animals, (2) preventing undue spillage so that consumption of cancer causing chemicals may be accurately measured and (3) preventing contamination of the feed by feces or urine containing microbiologival pathogens and carcinogenic metabolites which distort the research results. However, due to the particular design of these earlier mouse feeder embodiments, only a specially prepared particle-sized feed could be used to prevent bridging or caking, such caking preventing feed flow. This feed is economically impractical to obtain in the large quantities which are needed.